U.S. Pat. No. 4,555,876, as owned by the assignee of this invention, discloses therein an apparatus for handling lead frames so as to permit them to be supplied to and removed from a blasting chamber to effect removal of undesired resin such as flash and burr from around the contacts. In this known apparatus, a plurality of lead frames are stacked within a cassette, and a plurality of cassettes are mounted around the periphery of a rotatable turntable. The lead frames are individually dispensed from one of the cassettes at a predetermined location, with the lead frames being supplied individually and sequentially onto a conveyor which then feeds them into the inlet end of a blasting chamber. The individual lead frames are supported on side-by-side conveyor belts as they are transported through the blasting chamber so as to permit removal of resin burr and flash. The individual lead frames, when leaving the blasting chamber, are then transferred to a removal conveyor which moves the lead frames to a discharge location whereat they are sequentially displaced and loaded into a cassette which is also mounted on a turntable. When the cassette is filled, the turntable is rotated to bring an empty cassette into the loading position so as to permit the operation to continue.
While the apparatus of the aforementioned patent, and variations thereof, has proven to operate in a desirable manner, nevertheless such apparatus possesses features which the assignee considers less than optimum. For example, the individual and sequential transfer of the lead frames from the supply cassette to the input conveyor, and the subsequent individual and sequential transfer of the lead frames from the outlet conveyor to the outlet cassette, involves mechanisms which are relatively complex in view of their structures and motions. Further, this known apparatus can not be readily adjusted to handle lead frames of different size, specifically of different widths. Further, the input and output conveyors associated with the blasting chamber do not always provide for optimum transverse confinement and hence positional control over the lead frames as they are supplied into or moved away from the blasting chamber.
In addition, a difficulty encountered in handling lead frames is the distortion which these units undergo. Since lead frames are very thin, they are easily distorted and this hence makes handling and transferring of such units difficult, and in some instances the handling and transferring of the lead frames increases the distortion such that they can not be satisfactorily used.
Accordingly, it is an object of this invention to provide an improved guiding and feeding device which is particularly suitable for handling lead frames, such as for permitting individual and sequential transporting of such lead frames into and away from a blasting chamber. The arrangement of this invention is particularly desirable in that it permits the use of movement devices and motions which possess greater structural and operational simplicity and at the same time provide more accurate and desirable control over the lead frames being transported. The arrangement also desirably adapts and readily adjusts to changes in the size of the lead frames without requiring extensive reconstruction or shut-down of the apparatus.
The improved guiding and transporting arrangement of this invention employs opposed side rails which have longitudinally extending guide structure associated therewith for slidably accommodating a lead frame between the guide rails, which guide rails are slidably supported on transversely extending guide rods, and are drivingly coupled together by a threaded screw arrangement which can be readily driven so as to accurately and efficiently move the guide rails inwardly and outwardly to adjust the spacing therebetween. A conveyor is disposed for cooperation with the guide rails and is disposed below the lead frames so as to drivingly displace the lead frames longitudinally along the guide rails.
The improved guiding and transporting arrangement of this invention, particularly when used for supplying lead frames to a blasting chamber, additionally has transfer means associated therewith to individually and sequentially supply the lead frames to the guiding device. This transfer means permits individual lead frames to be supplied from a stack into a mechanism which engagingly supports the individual lead frame and then movingly transfers it linearly along a path which is aligned with the guideway so as to effect transfer of the lead frame into the guideway for engagement with the conveyor associated therewith. The transfer mechanism employs a first displacing mechanism which vertically lifts the stack of lead frames so that the uppermost one is disposed between an opposed pair of supporting elements which move transversely inwardly for engaging the uppermost lead frame, with the uppermost lead frame then being slidably displaced linearly into the guideway by a drive unit, such as a reciprocal ram.
A further object of the improved lead frame feeding device of this invention is its ability to handle, and in effect straighten the distorted lead frames so as to minimize the rejection rate of such units following processing thereof.
The improved guideway arrangement of the present invention is also associated with the discharge end of the blasting chamber, which guideway again employs opposed side rails which are slidably and adjustably supported for permitting the spacing therebetween to be readily adjusted to slidably accommodate the desired width of lead frame. There is additionally provided, in association with this guiding arrangement, an appropriate transfer mechanism which individually and sequentially transfers the lead frames transversely relative to the guideway so as to permit further handling thereof, such as the stacking of such lead frames for storage within a cassette.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.